Alexis Sanchez's hat-trick at Leicester was the sign of a "world-class" player back to his best, according to Arsene Wenger.
The Chilean broke his drought for the season to help Arsenal end City's unbeaten start with a 5-2 win at the King Power, Theo Walcott and Olivier Giroud scoring the other goals.
Wenger predicted Sanchez's revival in the run-up to the game, and afterwards told Sky Sports: "It was coming, you could feel one day it would work. Let's hope that's a confidence factor that will be beneficial in the future."
The Arsenal boss expanded on the theme at his post-match press conference, saying: "He is back to his level. He won a big competition with Chile - the Copa America. I think as well mentally to adjust to the game on a mental level takes some time.
"I could see in training a different player in the last week or two and he has shown that today. I believe going forward he always looked dangerous."
Asked whether he considered Sanchez world-class, a topical term given Alex Ferguson's recent claim that he managed just four such players at Manchester United, Wenger said. "I think so.
"I think I have plenty of players that are world class. You have to understand the definition of that but overall he is a striker who is mobile and works hard for the team. When the team plays well he can score goals."
Arsenal are now just three points behind new leaders Manchester United, who took advantage of Manchester City's defeat at Tottenham and visit the Emirates next weekend.
Wenger said: "You want the distance to the leaders to be as minimal as possible and [City's] was a positive result for us, but it's very tight and you're in danger everywhere in this Premier League."
Wenger confirmed Mathieu Flamini suffered a hamstring injury on his first league appearance of the season and said he hoped Francis Coquelin would be fit to face Olympiakos on Tuesday.